A conventional thermoelectric device uses a class of materials known as thermoelectric materials that exhibit thermoelectric effects such as the Thomson effect, the Peltier effect, and the Seebeck effect to directly transduce thermal energy to electric energy flow and conversely. The thermoelectric material is formed such that there are two opposing ends, wherein the two opposing ends have thermal and electrical contacts for the generation of power using the Seebeck effect, the thermoelectric material is placed in a thermal gradient with one end being at a lower temperature and the other end being at a higher temperature. Due to the temperature difference between the two ends, the thermoelectric material generates an electrical current and voltage.
FIG. 1 is a simplified perspective illustration that is consistent with prior art wherein a portion of the top substrate has been cut away exposing the internal structure of the module 100. Heat flows vertically through module 100 whereas current flows up and down in each thermocouple which are connected in series throughout the module. Conventional thermoelectric modules use a plurality of thermoelectric devices 102, exemplified by thermoelectric couple 104 and 106, wherein both P-type thermoelectric material 110 and N-type thermoelectric material 108 are used. When conventional P-type thermoelectric material 110 and N-type thermo electric material 108 are subjected to the ame temperature gradient, N-type and P-type thermo electric materials generate electrical currents that are in opposite directions of each other. Conventional thermoelectric modules, as illustrated in FIG. 1, use this property by assembling alternating P-type and N-type materials 110 and 108 sandwiched between a common hot plate 112 and common cold plate 114 while electrically connecting them in a series circuit using a first and second plurality of metal straps of which metal straps 120 and 122 are examples. Heat flux, shown by arrows 124 and 126, pass through the P and N thermoelectric material in parallel while electrical power is generated in series wherein the voltage generated by the alternating P and N type thermoelectric materials 108 and 110 are additive.
Conventional thermo electric modules, illustrated by module 100, have several inherent problems with their design and function. Conventional designs require both N and P type devices such as thermoelectric couple 104 and 106 as previously described. The P and N thermo electric materials, for example thermoelectric materials 110 and 108, must be electrically matched often requiring different physical sizing of the individual thermoelectric materials. Since the P and N type devices are electrically coupled in series in conventional module designs, each device must generate the same individual current for optimal module performance. The thermoelectric material used in the making of the P and N type devices typically have inherently different current generation capabilities that can be alleviated by making the P and N type thermoelectric materials different sizes. The sizing of the thermo electric materials makes the module design and manufacturing more complex and expensive. Consequently, most module manufacturers find it more cost effective to make P and N devices the same size which leads to suboptimal module power generation.
The P and N devices must also be matched for thermal expansion. P and N type devices may each be made of different semiconductor material that have differing thermal expansion coefficients which causes mechanical stresses resulting in reduced module reliability and usable life times.
The temperature dependent performance of both the P and N thermoelectric materials must be matched for optimal performance. However, the peak-power operation temperature for P and N type thermoelectric materials can differ leading to suboptimal power performance when forced into a common module.
The manufacture of current module designs requires the selection and precise placement of alternating P and N type thermoelectric materials in the module array. This requires careful tracking of two types of thermoelectric materials (P and N type materials) that build the thermoelectric devices and their placement since a single misplaced thermoelectric material and/or device would impair module functionality. Different contact structures bonding the P and N type devices may also be required which makes the manufacturing process more complex and expensive.
It can be readily seen that the present design of thermoelectric devices, the design of thermoelectric modules, and the methods to make both have severe limitations and problems. Also, it is evident that the present fabrication methods for building thermoelectric devices and modules are complex and subject to reliability failures. Therefore, an article, design, and method for assembly of thermoelectric devices and modules that is cost effective, simplistic, and manufacturability in a high volume manufacturing setting is highly desirable.